Determine whether EBV antibody levels can be used to predict the change of a child developing Burkitt's lymphoma. This study will include a cohort of 40,000 children from the West Nile district. Search for environmental conditions in Uganda which could be associated with Burkitt's lymphoma. Investigate perinatal EBV infection in Uganda. In Lyon, search for immune complexes in sera obtained in Uganda. In Lyon, perform EBV antibody titers on sera from Burkitt's lymphoma cases and controls. To establish Burkitt's lymphoma incidence and registration in the North and South Mara districts of Tanzania for baseline information prior to malaria suppression in North Mara in 1977. The suppression studies are to be funded entirely by WHO in Geneva. Etiological studies on nasopharyngeal cancer: Production and standardization of EBV and NPC antigens; Studies of genetic markers in NPC patients and controls.